A method for reformer tube in situ inspection radius calculation

ABSTRACT

A method for inspecting a reformer tube for chemical processing for damage such as creep and metal dusting. The method includes the steps of focusing a coherent light beam onto an interior of a tube or piping and detecting at least a portion of a reflection of the light beam from the tubing by converting the detected light beam into an electrical signal and the processing of the electrical signal to determine a radius of tube under-going in situ inspection.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present patent application is related to our copendingapplication entitled “A Method For Reformer Tube In Situ InspectionRadius Calculation,” U.S. application Ser. No. 10, ###,### filed12/25/2003, which is incorporated by reference as if fully set forthherein.

BACKGROUND OF INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to inspection of materials, andmore particularly to the inspection of the surface of materials forcreep, metal dusting, irregularities, and manufacturing flaws. Withstill greater particularity the invention pertains to the inspection ofthe interior of cylindrical surfaces such as reformer tubes used inchemical processing.

[0004] 2. Description of the Related Art

[0005] Reformer tubes are used in many chemical processes. Examplesinclude tubes used to produce ammonia, methanol, hydrogen, nitric andsulfuric acids, and cracking of petroleum. Reformer tubes, also calledcatalyst tubes, are one of the highest cost components of such plantsboth in capital and maintenance. A typical installation consists ofseveral hundred vertical tubes. These tubes represent a significant costfor replacement and can be a major source of plant unavailability ifunplanned failures occur.

[0006] Such tubes are frequently subjected to pressure changes andcontact with corrosive substances. Under such situations creep, metaldusting, and surface irregularities frequently develop. If leftuntreated, creep will develop into cracks that will propagate leading tofailure of the tube.

[0007] The plant operator is faced with balancing production needsagainst tube life and risk of tube failure. The Inner Diameter (ID) ofthese reformer tubes is generally between 76 mm (3.0 inches) and 127 mm(5.0 inches). During plant operation the catalyst filled tubes areexternally heated to allow the reforming reaction to occur. One of themajor concerns in plant operation is that the reformer tubes operate atan elevated temperature such that they are susceptible to a failuremechanism referred to as “creep”. This condition exists due to theelevated temperatures and stresses imposed by internal pressure, thermalgradients, and mechanical loading cycles. Being able to identify andlocate such damage in its early stages is essential for optimizing plantoperation.

[0008] Conventional Nondestructive Examination (NDE) inspectiontechniques currently applied to reformer tubes are geared to findingcreep damage in the form of internal cracking. However, with the trendtowards larger tube diameters and longer intervals between turnarounds,the detection of such defects may not allow for sufficient time forforward planning of tube replacements. Also, such “end of life”techniques do not allow any differentiation between the “good” tubes.Early detection of underutilized tube life can prevent the lostopportunity on both unrealized production through running them too cooland tube life “giveaway” if good tubes are discarded prematurely.

[0009] Typically, destructive testing is used on a small number of tubesremoved from the reformer to try and determine the absolute liferemaining. Whatever the method is used, the results are used on a samplesize that is not statistically valid. It is preferable that all thetubes be surveyed with a NDE technique to characterize their relativecondition in order to make sense of the absolute condition assessmentprovided by the destructive testing.

[0010] Reformer tubes undergo creep strain, in the form of diametricalgrowth, on the first day that they are fired. The ability to accuratelymeasure and record this growth means that the tubes' condition can bemonitored on day one. Therefore, not only can individual tubes beretired from service at an appropriate time, but also the reformer as awhole can be assessed for performance.

[0011] Another problem that can occur in reformer tubes is metaldusting. Metal dusting is a condition where the process stream attacksthe interior of the reformer tube with subsequent, significant metalloss. This can be severe enough to be the life limiting condition forthe tube. Typically, the metal dusting damage is limited to a 360°circumferential band around the catalyst tube's interior surface wherethe critical temperature range exists.

[0012] External diameter measurements have been used but they arelimited as the automated devices only measure across one diameter andare often access-restricted by tube bowing. Manual measurements are tootime consuming to provide more than a few readings per tube. No externalmeasurement method can provide diameter growth data at or through thereformer refractory. External measurements are inherently less preciseas they are based on a cast surface rather than the internal machinedsurface and do not take into account the effects of oxide shedding. Themost accurate growth measurements are obtained when ‘as new’ baselinedata has been taken prior to the tube being fired for the first time.However, if this is not available by using the top portion of the tubethat is operating outside the creep temperature as a reference diameter,the growth profile of the tube can be determined at any stage in itslife.

[0013] Accordingly, there is a need for an automated method andapparatus capable of examining the internal surfaces of reformer tubes.The method should be nondestructive and provide both absolute andrelative information on tube profile.

SUMMARY OF INVENTION

[0014] The present invention has been made in view of the abovecircumstances and has as an aspect a method for inspecting a reformertube for chemical processing for damage such as creep and metal dusting.The method includes the steps of focusing a coherent light beam onto aninterior of a tube or piping and detecting at least a portion of areflection of the light beam from the tubing by converting the detectedlight beam into an electrical signal and the processing of theelectrical signal to determine a radius of tube under-going in situinspection.

[0015] An embodiment of the invention employs a solid-state laser diode.A focusing lens is located in front of the diode to focus the laser at aspot on the surface of the tube to be inspected. The diode and focusinglens are rotatable within the tube to allow the spot to form a ring asthey are rotated. As the probe moves through the tube the spot scans theentire surface. A photo detector is arranged behind an imaging lens todetect the intensity of the spot. Both the detector and the imaging lensrotate in the same fashion as the laser diode and its focusing lens. Theoptical paths are selected so that the diode, photo detector and surfaceof the tube form a triangle. The distance between the detector and diodeis fixed. This results in the reflected spot moving on the surface ofthe photo detector in proportion to the distance to the internal surfaceof the tube. Signal processing means can then use that information toreconstruct a three dimensional image of the internal surface of thetube. The image may either be displayed on a monitor or printed forlater review.

[0016] With present technology a 15-meter tube can be inspected withinthree minutes. An inspection such as this will provide over 1,000,000radius readings. The method provides means to compress this informationto allow easy manipulation and analysis.

[0017] A further aspect of the present invention employs a laser orlight emitting diode (LED) and a cone shaped reflector to project a ringof illumination on the interior of the tube to be inspected. Acharge-coupled device (CCD) is arrayed so as to scan the ring and reportthe reflectivity and profile. Signal processing circuitry reconstructsan image of the interior of the tube.

[0018] The use of the internal laser mapping technique is not onlyuseful in preventing tube failure but has huge potential in optimizingproduction from the whole tube set without sacrificing reliability.

[0019] Additional aspects and advantages of the invention will be setforth in part in the description which follows, and in part will beobvious from the description, or may be learned by practice of theinvention. The aspects and ad vantages of the invention will be realizedand attained by means of the elements and combinations particularlypointed out in the appended claims.

[0020] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly described, thepresent invention can be characterized according to one aspect of theinvention as comprising a method for the in situ inspection of areformer tube or similar type tube or piping used in chemical processingfor damage such as creep and metal dusting. The method includes thesteps of focusing a coherent light beam onto an interior of the tube anddetecting at least a portion of a reflected light beam and converts thedetected light beam into an electrical signal and further processes theelectrical signal to determine a radius of the tube.

[0021] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate several embodimentsof the invention and together with the description, serve to explain theprinciples of the invention.

[0023]FIG. 1 is a block diagram of an embodiment of the Invention;

[0024]FIG. 2 is diagram of the optical components of the FIG. 1embodiment;

[0025]FIG. 3 is a perspective detail view of the probe of the invention;

[0026]FIG. 4 is a block diagram of an alternate embodiment of theInvention;

[0027]FIG. 5 is diagram of the optical components of the FIG. 4embodiment.

DETAILED DESCRIPTION

[0028] Reference will now be made in detail to the present embodimentsof the invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts (elements).

[0029]FIG. 1 is a block diagram of an embodiment of the invention.Components may be either hardware components or software modules asdescribed below. The probe includes a light source 1.

[0030] The purpose of the light source 1 is to project a spot of lighton the surface (not shown) to be inspected. Light source 1 is typicallya laser diode or light emitting diode (LED). A light source controller 2is connected to light source 1. Controller 2 sets and controls theoptical power level of light source 1. The power level may either befixed or varied to produce a preset signal level.

[0031] A position sensitive photo detector (PSD) 3 is situated so as todetect the spot made by light source 1. Photo detector 3 may be alateral effect photodiode, photodiode array, or charge coupled device(CCD). This description assumes the device chosen for 3 is a lateraleffect photodiode. Detector 3 may have either one or two axes, dependantupon the specific measurement geometry. In this description only asingle axis detector and associated lens (not shown) is used. Similarlya 2D detector may be used for 3 if the light beam from light source 1 isrotated, by means of a rotating mirror, and detector 3 is fixed. Anamplifier filter 4 is connected to detector 3. Amplifier/filter 4converts the small signal currents generated by detector 3 intovoltages. A filter sets the bandwidth of the system.

[0032] The required bandwidth is determined by a combination of thespeed of probe spin and the required sample rate. Amplifier and filtermay be combined into a single unit by inserting active components into adifferential amplifier to produce an active filter. A suitable amplifiermay be an integrated circuit differential amplifier such as a AD712. Afeedback path is provided between amplifier/filter 4 and light sourcecontroller 2 to allow control of light source 1 dependent upon theintensity of signal received at detector 3. One or more gain systems 6may be connected to the output of amplifier/filter 4.

[0033] This embodiment shows 2 gain systems (5 and 6) each providing adifferent level of gain. The addition of one or more additional gainsystems increases the dynamic range of the system and allows rapidchanges of surface reflectivity to be measured. The outputs of theseveral gain stages are recorded simultaneously, and the largest valuethat is below saturation is used. Several gain systems may be connectedin parallel to provide usable signals in all situations.

[0034] A normalization and synchronization processing circuit 7 isconnected to the output of gain system 6. The first function of system 7is to select the signal from multiple gain systems 6 with the maximumdynamic range without saturation. The second function is to convert theindividual detector readings to a calibrated measurement of the distancebetween light source 1 and the surface to be scanned. For a ED detectorthe calibration may be found by solving equation 1 as the follows:$\begin{matrix}{{Measurement} = {g \cdot \frac{v_{1} - v_{2}}{v_{1} + v_{2}}}} & {{EQ}.\quad 1}\end{matrix}$

[0035] In the equation 1, v₁ and v₂ are the current readings from eitherend of detector 3. (g) is a calibration function used to removenon-linearity in the detector and optics. (g) may be determinedempirically by scanning calibrated tube samples of various diameters andusing the resultant data points to find coefficients of the function(g). As an alternative to the calculation using (g) in the aboveequation, a lookup table with some form of interpolation may be used. Inorder to eliminate electronic drift the system periodically turns lightsource 1 off and measures electronic offset voltages. The offsetvoltages are then subtracted from subsequent readings made with lightsource 1 on. Normalization and synchronization processing circuit 8 alsomeasures the surface reflectivity. The reflectivity of the surface iscomputed from the detector signal level, gain, and light source powerlevel. Variations in surface reflectivity can provide useful informationabout the surface. Normalization and synchronization processing circuit7 also collects data from a rotational encoder in 8. The correlation ofthe signals from encoder in 8 and from photo detector 3 assures equallyspaced samples around the circumference of a tube.

[0036] Two motors 11 and 12 move the probe. The first motor 11 rotatesthe probe within a tube. A motor drive circuit 13 controls motor 11.Encoder 8 is connected to motor 11 allowing determination of theabsolute rotational position of the probe. The output of encoder 8 isconnected to normalization and synchronization processing circuit 7. Asecond motor 12 provide axial positioning of the probe. A second motordrive circuit 14 controls motor 12. An axial incremental encoder 15connected to motor 12 provides information on the axial position of theprobe in the tube.

[0037] A system data storage display and control module 16 providesoverall control of the probe. Module 16 receives information on thedistance between light source 1 and the surface sought to be inspectedand surface reflectivity from normalization and synchronizationprocessing circuit 7. Module 16 also receives information about theaxial position of the probe from encoder 15. Module 16 controls therotational position of the probe in the tube by sending an on and offsignal to rotational motor drive circuit 13. Module 16 also controls theaxial position by sending on/off and forward/backward signals to axialmotor control circuit 14.

[0038]FIG. 2 is diagram of the optical components of the FIG. 1embodiment. A light source 1 produces beam of light. Light source 1 isusually a diode laser but could be a light emitting diode in specialapplications. A collimating lens 21 downstream of light source 1converts the light emitted by light source 1 into a collimated beamwhich does not spread to any appreciable extent over the inspectionrange 22″-22″. The beam produces a target spot 22 where it impacts thetarget surface 23. A photo detector 27 is mounted at an angle to theoptical train of components 1, 21, and 22. The angle is detected suchthat the imaged spot at 26 is in focus over the measurement range 22″ to22″. Photo detector 27 is usually a lateral effect photodiode array orcharge coupled device (CCD) photo detector. Photo detector 27 may eitherbe a one dimensional (1D) or two dimensional (2D) device. If photodetector 27 is a 2D device additional information may be generated atthe expense of greater bandwidth. An imaging lens 24 is mounted in frontof photo detector 27. Imaging lens 24 projects an image of the surfaceof target 23 onto photo detector 27. The image projected onto photodetector 27 includes an image 26 of the spot 22 where the collimatedbeam impacts the target. The position of imaged spot 26 varies with thedistance from light source 1 to target 23 due to parallax. If, forexample, the surface of target 23 is at 22″ the imaged spot is at 26″.Similarly, if the target is at 22″the imaged spot will be at 26″. Theresult is that imaged spot 26 moves back and forth across the surface ofphoto detector 27 in an amount relative to the distance between targetsurface 23 and light source 1. Photo detector 27 thus generates anelectrical signal containing information about the distance between 1and 23.

[0039] The complete optical system, as described, is rotated around thecentral axis of the probe in order to scan the complete circumference ofthe tube. Other embodiments modify the basic optical system to reducethe need for slip rings for the electrical signals required by the laserdiode and detector. By locating the laser diode source and collimatinglens on axis with the probe longitudinal axis and using a rotating 45°mirror to deflect the light beam at a right angle to the probelongitudinal axis, the beam can be made to scan the circumference of thetube. A second mirror and imaging lenses are also rotated with the firstmirror, to form an image of the light spot onto a stationary 2D PSD.This approach has the advantage of eliminating slip rings from theprobe. The disadvantage is that the 2D PSD provides 4 outputs instead of2, and requires more processing to compute the radius data. Anotherdisadvantage of this method is that a transparent tube or windows in thehousing are required to support the laser diode and detector, whilestill allowing a light path. The window or transparent tube are subjectto scratches or dirt which provide reflection paths for light leakagebetween the laser diode source and the detector. These light leakagepaths cause errors in the radius measurement. Also, the electrical wiresnecessary to connect to either the diode or detector must cross the pathof the light beam at some point in the rotation of the lens/mirrorassembly. Other variations of the optical arrangement are possible. Theembodiments described herein are not intended to limit the scope of theinvention, but rather are for illustrative purposes.

[0040]FIG. 3 shows a detailed profile view of the probe of an embodimentin this invention. The probe consists of a rotating optical head 30mounted to a body 31. The relative size of the reformer tubes presentother challenges to laser-optical probe design. Previous probes of thistype have been for smaller diameter tubing, up to 2-inches in diameter.For larger diameter tubes, such as reformer tubes, the weight andinertia of the probe and its rotating components must be reduced to makethe approach practical. In one embodiment of the system, the probe head30 is spinning at 1800 rpm. Replacing a metal spinning head with onemade of Delrin™, an engineering plastic made by Dupont, provides weightand inertia reduction while maintaining structural strength, thermalstability, and impact resistance.

[0041] The probe body 31 is made relatively small compared to thediameter of the reformer tube. This allows weight reduction, and has thebenefit of allowing the same probe body to be used in several differenttube sizes by changing the centering spring assemblies, and the probehead. Weight reduction is important in the reformer tube applicationbecause the probe is drawn through the tube by a motorized positioningsystem. Reducing the weight reduces the size and cost of the positioningsystem.

[0042] A tether and electrical connections are made to the probe throughconnector 32. Electrical connections between the connector and theoptical head are made through the probe body by means of an internalslip-ring. Probe rotation is by means of a motor inside probe body 31.Centering rings 35 are spring loaded arms with non-metallic wheels tohold the probe in the center of the tube, and allow for axial motionthrough the tube.

[0043] Reformer tubes are made of special alloys to withstand thetemperature and pressure regimes to which they are subjected. Duringnormal operation, portions of reformer tubes operate at or near thestructural stability limit of the tube metallurgy. If the probe leavesany traces of other metals on the inner tube surfaces, such as aluminumor lead, the traces of these metals will enter the pores of the tubewall and cause rapid cracking and failure of the tube.

[0044] Therefore, it is important that only non-metallic components beused where the probe is in contact with the tube surface. The probe'scentering spring mechanism 35 contacts the sides of the tube with wheels36 made from Delrin™, an engineering plastic with metal-like properties.

[0045] One of the problems that affects accuracy in PSD based lasertriangulation systems is when unintended reflections cause additionallight to impinge on the sensor. These reflections arise when lightreflects from the surface being measured, bounces off other surfaces andenters the detector from various angles. Because the PSD sensor measuresthe centroid of the light imaged on its surface, reflections cause askewing of the image centroid. The present invention minimizesreflections by placing the laser 37 at the front of the probe head andin front of the detector 38. In contrast to designs with the laserbehind the detector, this reduces the exposure of the detector to lightreflections off the probe head 30, body 31, and centering springassemblies 35.

[0046]FIG. 4 is a block diagram of an alternate embodiment of theinvention. This embodiment projects a ring of light onto the interiorsurface of the reformer tube. The ring is then scanned with an array oflight sensors to produce and reconstruct an image of the interior of thetube.

[0047] A light source 40 is connected to a power controller to maintaina light level sufficient to be sensed by an image detector. Typicallylight source 41 is a laser diode with output in the infrared or visibleportion of the spectrum. A light detector 42 is positioned in such amanner as to view an image of the ring of light. Light detector 42 is atwo dimensional array of photosensitive cells. Most commonly detector 42is a Charge Coupled Device (CCD) array of photocells. Such arrays arecommonly used in video cameras. Array 42 is divided into individualpixels each represented by an X coordinate and a Y coordinate. Thesignal from each pixel is proportional to the intensity of light fallingon that pixel. The detector is controlled by a timing and control module43. In general, module 43 scans the array in a line-by-line fashion.Each individual line is moved to an output register. The individualpixels are then shifted out in a serial operation. The CCD array is ofthe Frame Transfer type which uses two identical CCD arrays, one forscanning and one for storage. The second array is shielded from lightand acts a buffer to allow reading an image while a second image isbeing formed on the first array. A typical sensor is a 512×512 arrayhaving 262,144 elements or pixels. Typically, there are additional lightshielded pixels in the array which provide buffering of the activepixels. This increases the number of total pixels which must be read.

[0048] A typical 512×512 array requires a clock speed of 80 Mhz to readout with time for the buffer pixels, transferring the frame, etc., for a120 Hz frame rate. Some arrays have a split output structure, so thattwo pixels are read at a time. This reduces the clock rate to 40 Mhz,but requires two parallel output processing channels. In testedprototypes the ring image has a thickness of 3-5 pixels. At the maximumradius the number of pixels actually used is provided by equation 2 asfollows:

2·π·r·5≅8 k pixels  EQ.2

[0049] Where r, at the maximum radius is 256 for a 512×512 array. Inother words each frame will hold about 8k pixels of useful information.

[0050] During use, array 42 converts the image to an array of intensityvalues. The Analog to Digital Converter 44 connected to Array 42converts this analog signal to a digital one. An eight-bit A to Dconverter has been found suitable for 44. The signal next goes to aLook-Up-Table (LUT) 45 to convert the Cartesian X, Y coordinatesreceived from the Timing and Control Module 45 into radial coordinatesr,_(t). LUT 45 may be a logical array or an addressable device such thatwhen an X, and Y address is input, a value for r and φ is provided. Thismay be done with non-volatile memory devices such as ROM, PROM, EPROM,EEPROM, flash memory, or a volatile memory such as static or dynamicRAM. The speed of operation required for this embodiment dictates theuse of volatile memory, such as synchronous RAM. The access time must beunder 30 nanoseconds for a 512×512 array. A 256 k×18 device provides 9bits each for r and φ. For a 10-bit φ, the MSB of the Y address valuecan be added to φ to form 10 bits. A 9-bit φ is used for 360 points perrotation, 10 bits for 720 points per rotation, for ½° resolution.

[0051] The X and Y address of each pixel is fed to the address lines ofthe LUT at the same time that the value of intensity for the pixel isavailable from the A to D converter 44.

[0052] Because LUT 45 is a volatile memory device, it must be loadedwith the lookup values before use. This may be done on power up of DSP50 or host PC 51. LUT 45 is programmed with the corresponding r and φfor each X and Y address of sensor 42 according to equation 3 asfollows:

r=SQRT (X ² +Y ²), φ=tan⁻¹(Y/X)  EQ. 3

[0053] The intensity value from array 42 and the r, φ values from LUT 45are sent to a Data Range Control module (DRC) 46. DRC 46 reduces theamount of data used in further processing steps. The actual image fromarray 42 includes only about 8 k of pixels out of a typical 256 k pixelsin a 512×512 array. The pixels of interest are in a circular area in theouter third of the array. The definition of the pixels of interest t isr>r_(t) where r_(t) is the radius threshold value and is the minimum rvalue of interest. No image data ever occurs at r-values less thanr_(t). DRC 46 includes logic circuitry which only passes to FIFO 47 theinformation of interest i.e. r>r_(t).

[0054] Even with the use of DAC 47 there are still too many pixelswithout useful information for easy processing. For example in a 3-in IDpipe with a probe measuring range from 2.25 in to 2.75 in. radius and a512×512 array the measuring range will cover 85 pixels with r having arange of from 171 to 256. If r_(t) is set to 170 there are still over170,000 pixels per frame to be processed. Only the pixels that areilluminated by the light source 40 provide useful information. Sinceonly pixels with intensity over a certain threshold are of interest thatfact may be used to eliminate surplus pixels. A high-speed comparator 48is used to compare the intensity value of each pixel with a thresholdvalue I_(t). The output of comparator 48 triggers the data selection topass only the data including r, φ, and I, where I is greater than thethreshold I_(t). This reduces the data sent to FIFO to about 8 k pixels.The threshold value I_(t) is set with a DAC device 49. DAC 49 is setfrom the host system via the DSP controller 50 during calibration.

[0055] Since the actual data rate is greater than 40 MHz accordingly; aFIFO 47 is used to buffer the data at that rate. Data entering FIFO 47clocks at the scan rate of the array 42 but is sporadic and has manygaps due to the action of the data selection effect of DRC 46 andcomparator 48. FIFO 47 buffers the data for DSP 50, which is thus ableto read the data at a slower rate. DSP 50 must still process all 8 k ofdata in under 8.3 milliseconds in order to process 120 frames/sec. FIFO47 will buffer one frame of data for an 8 k FIFO or two frames for a 16k FIFO.

[0056] The Digital Signal Processor (DSP) 50 performs the actualcomputation of the radius of the tube by finding the centroid of theimaged light on each radial spoke φ_(k) where k indexes the anglethrough 360 or 720 increments depending on the resolution. The centroidfor each radial spoke φ_(k) is computed according to equation 4 asfollows: $\begin{matrix}\frac{\sum\limits_{i}\quad {r_{i} \cdot I_{i}}}{\sum\limits_{i}\quad I_{i}} & {{EQ}.\quad 4}\end{matrix}$

[0057] Where r is the radius value from 0 to 255 for a 512×512 array,and I is the corresponding intensity value for that pixel, i is theindex value for the array of points comprising the radial spoke. Inpractice, i starts at a radius much larger than 0 since the image is setin the outer third of array 42. A DSP 50 of sufficient speed can performthe division and provide the radius value directly. If a lower speed DSP50 is used it can compute the numerator and denominator of the aboveequation and provide the values as separate outputs. A post processingoperation in host PC 51 computes the actual radius value and convertsthe output to engineering units such as inches or millimeters.

[0058] The processed data is sent to host PC 51 via a high-speedinterface; suitable methods include serial interfaces such as RS232,RS485, USB, or IEEE-1394 (Firewire) or parallel interfaces such as a PCparallel port or EPP.

[0059] Host PC 51 receives the data from the probe processing system,and does any post processing of the data and formats it for storage onhard disk or removable media storage and displays the data on a graphicsscreen.

[0060]FIG. 4 illustrates an implementation having a single processingchannel. For an image sensor with a dual output structure, anotherchannel of processing is added with another A/D converter, LUT, DataRange Controller, comparator, and FIFO.

[0061]FIG. 5 is a front elevation view of the optical system of the FIG.4 embodiment. The components are located in a tube 64 to be inspected. Alaser diode 61 is located at the center of tube 64 in such a manner thatthe light emitted by diode 61 is parallel to the axis of tube 64. Acollimation lens 62 is located on said axes to focus the light on theinterior surface of tube 64. A cone mirror 63 is located coaxial todiode 61 and lens 62 to form the light emitted from diode 61 andcollimated by lens 62 into a ring 65 on the surface of tube 64. Mirror63 is preferably a parabolic conical mirror to aid in focusing the beamon the interior surface of the tube. An imaging lens 66 coaxial withdiode 61 lens 63 and mirror 63 is situated in such a manner as toproject an image of ring 65 onto the surface of an imagining array 67.Imaging array 67 senses the image projected onto its surface andconverts the image into electrical signals.

[0062] The above examples and embodiments are exemplary only theinvention being defined solely by the attached claims.

[0063] It will be apparent to those skilled in the ar_(t) that variousmodifications and variations can be made in the “A Method For ReformerTube In Situ Inspection Radius Calculation” of the present invention andin construction of this invention without departing from the scope orintent of the invention.

[0064] Other embodiments of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. It is intended that the specificationand examples be considered as exemplary only, with a true scope andspirit of the invention being indicated by the following claims.

[0065] Reference will now be made in detail to the present embodimentsof the invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts (elements).

1. A method for forming a profile of a radius of the interior of areformer tube comprising the steps of; projecting a light beam on aninterior surface of said reformer tube; collimating said light beam tofocus on the surface of said reformer tube; forming said collimated beaminto a ring on the surface of said reformer tube; projecting an image ofsaid ring onto a surface of a light detector and moving said ring alongan axis of said reformer tube; detecting light reflected from thesurface of said reformer tube; processing reflected light data collectedby the detector; and forming a radius profile.
 2. The method for forminga profile of the radius of the interior of a reformer tube according toclaim 1, further comprising the step of reflecting the light beam off ofa conical mirror surface.
 3. The method for forming a profile of theradius the interior of a reformer tube according to claim 2, wherein theconical mirror further includes a parabolic surface for maintainingfocus of the light beam on expected reformer tube diameter.
 4. Themethod for forming a profile of the radius of the interior of a reformertube according to claim 3, further comprising the steps of, reflectingthe light beam off a mirror, and rotating said mirror to produce a ringof light on the surface of said tube.
 5. The method for forming aprofile of the radius of the interior of a reformer tube according toclaim 3, further comprising the steps of, reflecting the light beam offthe surface of said reformer tube, and rotating a light source toproduce a ring of light on the surface of said reformer tube.
 6. Themethod for forming a profile of the radius of the interior of a reformerof a reformer tube according to claim 4, wherein the light source is atleast one of an LED, and a laser.
 7. The method for forming a profile ofthe radius of the interior of a reformer of a reformer tube according toclaim 5, wherein the light source is at least one of an LED, and alaser.
 8. The method for forming a profile of the radius of the interiorof a reformer tube according to claim 1, further comprising the stepsof, reflecting said beam off the surface said reformer tube, androtating an LED to produce a ring of light on the surface of saidreformer tube.
 9. The method for forming a profile of the radius of theinterior of a reformer tube according to claim 1, wherein the light beamis focused on an interior axis of said reformer tube.
 10. The method forforming a profile of the radius of the interior of a reformer tubeaccording to claim 9, further comprising the step of reflecting saidbeam off the surface of a conical mirror.
 11. The method for forming aprofile of the radius the interior of a reformer tube according to claim9, further comprising the step of reflecting said beam off the surfaceof the conical mirror with a parabolic surface for maintaining focus ofsaid beam on the expected reformer tube diameter.
 12. The method forforming a profile of the radius of the interior of a reformer tubeaccording to claim 9, further comprising the steps of, reflecting saidbeam off a mirror, and rotating said mirror to produce a ring of lighton the surface of said tube.
 13. The method for forming a profile of theradius of the interior of a reformer tube according to claim 9, furthercomprising the steps of, reflecting said beam off the surface saidreformer tube, and rotating an LED to produce a ring of light on thesurface of said reformer tube.
 14. The method for forming a profile ofthe radius of the interior of a reformer tube according to claim 9,further comprising the steps of, reflecting said beam off a mirror atthe surface said tube, and rotating an LED to produce a ring of light onthe surface of said reformer tube.
 15. The method for forming a profileof the radius of the interior of a reformer tube according to claim 9,further comprising the steps of, reflecting said light beam off thesurface said reformer tube, and rotating an LED to produce a ring oflight on the surface of said reformer tube.
 16. A method for forming aprofile of a radius of the interior of a reformer tube comprising thesteps of; projecting a light beam on an interior surface of saidreformer tube; collimating said light beam to focus on the surface ofsaid reformer tube; rotating at least one of the light source and amirror to scan the interior surface of the reformer tube; detectinglight reflected from the surface of said reformer tube; processingreflected light data collected by the detector; and forming a radiusprofile.